[Equest-users] How does eQuest designates total supply CFM for VAV units?

Wed Nov 30 09:21:19 PST 2016

Bikesh,

I would refer you to the following document:
https://energydesignresources.com/media/2651/EDR_DesignGuidelines_VAV.pdf?tracked=true

Happy hunting!

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DAVID W. GRIFFIN II
BEMP
ENERGY ANALYST
2505 E Parleys Way
Salt Lake City, UT 84109
Office 801.924.5028
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From: Bikesh Dahal [mailto:bdahal at EMEGroup.com]
Sent: Wednesday, November 30, 2016 10:16 AM
To: David Griffin II; Joe Huang; Nicholas Caton; equest-users at lists.onebuilding.org
Subject: RE: How does eQuest designates total supply CFM for VAV units?

Hi All,

I was wondering if anyone could provide some insight on to VAV systems in eQuest.
My modeling process:

Set min cfm/sqft=0.4 (As per guidelines)
Supply air to room air temperature difference of 200F

However, it seems as if supply cfm capacity mentioned in report (SV-A) is always high. However, maximum fan load in SS-H never seems to reach the peak (based on my kw/cfm input) .
This makes me think that eQuest is oversizing the supply cfm quite a bit. Could someone provide some guideline on this issue. Am I missing something?

Thanks,
Bikesh

From: Equest-users [mailto:equest-users-bounces at lists.onebuilding.org] On Behalf Of David Griffin II via Equest-users
Sent: Tuesday, November 29, 2016 6:04 PM
To: Joe Huang <yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>>; Nicholas Caton <Nicholas.Caton at schneider-electric.com<mailto:Nicholas.Caton at schneider-electric.com>>; equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Purpose of a DESIGN-DAY CLIMATE input?

Nick/Joe,

I have done some light research on the topic since DOE2.3 moves in the direction of utilizing DESIGN-DAY more rigorously; e.g. if you depend on the weather file for auto sizing in DOE2.3, your simulation takes twice as long. I would refer both of you to page 23 of the DOE2.3 Volume 6 "Design-Sizing Enhancements" where it appears the eQUEST team is attempting exactly what Joe previously mentioned.

Although I believe the CLIMATE input is still available in DOE2.3 it may be ignored by the new algorithm. Maybe Jeff H. can shed some light on this situation for us.

Sincerely,

[Image removed by sender. ARCH | NEXUS]<http://www.archnexus.com>

DAVID W. GRIFFIN II

BEMP
ENERGY ANALYST

2505 E Parleys Way
Salt Lake City, UT 84109

Office 801.924.5028

archnexus.com<http://www.archnexus.com>

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From: Joe Huang via Equest-users [mailto:equest-users at lists.onebuilding.org]
Sent: Tuesday, November 29, 2016 1:49 PM
To: equest-users at lists.onebuilding.org<mailto:equest-users at lists.onebuilding.org>
Subject: Re: [Equest-users] Purpose of a DESIGN-DAY CLIMATE input?

I think this is a case of DOE-2 still using an older procedure for the solar portion of the design day calculation.  Prior to 2006, ASHRAE used a relatively crude ASHRAE Clear Sky Model to determine the hourly profile of solar radiation for the design day.  That model assumes there are different sky conditions for different latitudes, etc.  In 2006, ASHRAE TC 4.2 (Climatic Information) carried out a project to develop an entirely new ASHRAE Clear Sky Model that's a parameterization of a detailed solar model developed by Chris Gueymard.

It would be nice if DOE-2 incorporates the new ASHRAE Clear Sky Model, which isn't terribly hard, but would take work. Besides, I'm under the impression that the vast majority of DOE-2 users don't do design day calculations but rather let the program autosize the equipment anyway!

Joe

Joe Huang

White Box Technologies, Inc.

346 Rheem Blvd., Suite 205A

Moraga CA 94556

yjhuang at whiteboxtechnologies.com<mailto:yjhuang at whiteboxtechnologies.com>

http://weather.whiteboxtechnologies.com for simulation-ready weather data

(o) (925)388-0265

(c) (510)928-2683

"building energy simulations at your fingertips"
On 11/29/2016 9:43 AM, Nicholas Caton via Equest-users wrote:
I have a question concerning doe2/eQUEST DESIGN-DAYs.

One of the keywords for DESIGN-DAY confuses me:  CLIMATE.  I have not been able to find this documented in the current doe2 reference manual or 2.1A engineering manuals.

It appears the CLIMATE keyword can accept one of three inputs:  "SUBARCTIC," "MIDLATITUDE," or "TROPICAL."  The default is MIDLATITUDE and does not appear to reference anything else.

[cid:image003.png at 01D24AF3.763C3010]

So I have a few questions:

1.       What is this input used for?  Does it help to determine solar angles during design day calculations?  Does it affect how other DESIGN-DAY inputs are interpreted?

2.       Since one of the options is named "MIDLATITUDE," my best guess is this is trying to establish in a loose sense which slice of the globe the weather station is located at for solar angle purposes.  From that guess, I googled the topic for a bit<http://www.lat34north.com/cities/CitiesLatitude.cfm> and came up with this framework:

a.       SUBARCTIC latitudes are > 66.5 or < -66.5  (Inside the Arctic circles - experiences days of complete daylight/darkness)

b.      TROPICAL is between -23.5 and 23.5 (Tropic of Capricorn/Cancer - experiences the sun traversing directly overhead)

c.       MIDLATITUDE = everywhere else

3.       I struggle however with the concept of a DESIGN-DAY input based on latitude, where

a.       The latitude is already a part of the weather file required for every simulation... and pulling the exact latitude would be more accurate anyway (I confess here I have never studied solar pathing in great depth - the problem may be simpler than I realize?).

b.      These bands alone don't give you enough information to know when you're in the lower hemisphere (where solar angles based on the day/month would be flipped)

c.       This leads me to question whether there's a (meaningful) difference in solar angles experienced for loads calculations when you use the weather file instead of DESIGN-DAY inputs.

d.      Alternatively, maybe the latitude IS pulled from the weather file for solar angle purposes so I'm completely on the wrong path as to the purpose/intent for the CLIMATE input.

Can anyone set me straight on this topic?

~Nick

[cid:image004.png at 01D24AF3.763C3010]
Nick Caton, P.E., BEMP
  Senior Energy Engineer
  Energy and Sustainability Services
  Schneider Electric

D  913.564.6361
M  785.410.3317
E  nicholas.caton at schneider-electric.com<mailto:nicholas.caton at schneider-electric.com>
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